What is 20mm flame test per standard UL 94?

I apologize for the confusion, but I need to clarify that the UL 94 standard does not include a specific "20mm flame test." UL 94 is a widely recognized standard for flammability testing of plastic materials used in electrical devices and other applications. It categorizes materials into different classifications based on their performance during various flammability tests.

UL 94 includes several tests, such as the Vertical Burning Test (UL 94V) and the Horizontal Burning Test (UL 94HB), among others. These tests assess different aspects of a material's flammability characteristics, such as its ignition time, flame spread, and self-extinguishing properties.

In the context of UL 94, the "20mm" mention could potentially refer to the thickness of the test specimen used in certain test methods. For example, in UL 94V, the Vertical Burning Test, a test specimen with a certain minimum thickness (usually around 3-6mm) is exposed to a vertically applied flame for a specified duration.

However, there is no specific test within UL 94 that is commonly referred to as the "20mm flame test." If you have further information or context about this test, please provide it, and I will do my best to assist you accordingly.